Ultherapy uses focused ultrasound to target the 4.5 mm SMAS layer, unlike RF...

https://fernandosnicethoughtss.scriblorax.com/posts/what-are-ultherapy-lines-and-why-do-they-matter

Ultherapy uses focused ultrasound to target the 4.5 mm SMAS layer, unlike RF which heats tissue around 40 to 45°C without deep reach. Standard HIFU often doesn’t go as deep as Ultherapy or is less precise